Catheters are flexible medical instruments intended for the withdrawal and introduction of fluids to and from body cavities, ducts and vessels. Catheters have particular application in hemodialysis procedures, in which blood is withdrawn from a blood vessel for treatment and subsequently returned to the blood vessel for circulation. Hemodialysis catheters can include multiple lumens, such as dual lumen or triple lumen catheters, which permit bi-directional fluid flow within the catheter whereby one lumen, the arterial lumen, is dedicated for withdrawal of blood from a vessel and the other lumen, the venous lumen, is dedicated for returning purified blood to the vessel. During some hemodialysis procedures, a multiple lumen catheter is inserted into a body, and blood is withdrawn through the arterial lumen of the catheter. The withdrawn blood is directed to a hemodialysis unit which dialyzes, or purifies, the blood to remove waste and toxins. Thereafter, the dialyzed blood is returned to the patient through the venous lumen of the catheter.
Generally, hemodialysis catheters are categorized as either chronic or acute in nature. Chronic catheters typically remain in place for extended periods of time, and may be implanted via surgical dissection. Acute catheters, by comparison, are designed to be placed in a patient under emergent circumstances in which speed of placement is desirable. Acute catheters typically remain in place for only a few days. As such, acute catheters are often more rigid than chronic catheters, given the urgency of placement.
In hemodialysis catheters, recirculation can occur when purified blood exiting the venous lumen of the catheter is withdrawn directly into the arterial lumen such that purified blood is returned to the dialyzer. As such, recirculation increases the time required to complete the hemodialysis procedure.